This is an application for a Clinical Associate Physician Fellowship supported by the General Clinical Research Centers Branch of the National Institutes of Health. The proposed studies involve surveys of nursing home residents and hip fracture patients to determine the frequency of vitamin D-deficient osteomalacia, by correlating blood 25-hydroxyvitamin D levels, bone mass, and bone histology. Companion studies are proposed to evaluate the effects of specific vitamin D metabolites in patients with osteomalacia or osteoporosis, by measuring calcium balance, radioactive calcium turnover, bone histology, and bone mass. The studies will be carried out on the Ward 4 General Clinical Research Center and in the Departments of Medicine and Orthopaedics at the Massachusetts General Hospital.